Obesity is one of the most prevalent health problems in the world, particularly if it is considered in relation to the increase in prevalence of associated diseases such as type II diabetes, dyslipemia and hypertension. Obesity is the consequence of increased adipocyte size as well as development of new fat cells. Adipogenesis results from a cascade of genetic events in which CCAAT/Enhancer Binding proteins (C/EBPs) play a key role. Disruption of the C/EBP2, C/EBP4 or C/EBP1 gene in mice causes defective development of adipose tissue. During adipogenesis the activation of a specific subset of genes and silencing of the remainder takes place. As genes are silenced, the extent of chromatin condensation increases, and extended regions of DNA are packaged in transcriptionally inactive form: heterochromatin. The organization of genes into heterochromatin is one of the mechanisms that control its silencing. Intriguingly, C/EBP2 rapidly relocalizes in heterochromatin upon hormonal stimulation. C/EBP2, C/EBP4 and C/EBP1 also concentrate in heterochromatin upon induction of preadipocytes to differentiate into adipocytes. We hypothesize that C/EBP2 may play a role in the regulation of gene silencing during cellular differentiation. Thus the specific aims of this project are to investigate in preadipocytes and during adipogenesis: a) mechanisms that regulate the formation of homo- and heterodimers of C/EBP2, b) mechanisms that control the subnuclear distribution of C/EBP2, and c) the role of C/EBP2 in gene expression by determining the position of C/EBP2 target genes with respect to heterochromatin. Our studies will provide insight into the understanding of the mechanism that controls the nuclear redistribution of C/EBPs and their role in the heterochromatic nuclear compartment. Improvement of our understanding of adipogenesis is important, for it will ultimately contribute to the development of new therapeutic strategies for obesity and related disorders. This study extends new approaches initiated by Dr. Piwien-Pilipuk when she was a postdoctoral trainee in Dr. Schwartz's lab. Now that Dr. Piwien-Pilipuk has returned to Argentina and is establishing an independent lab, the collaborative interactions between these PI's through the proposed project, involving visits to Dr. Schwartz's lab by Dr. Piwien-Pilipuk and at least one of her graduate students during the course of this project, will facilitate Dr. Piwien-Pilipuk's career development, in addition to adding to understanding of the regulation of C/EBP beta through collaborative papers. This research will be done primarily at Instituto Leloir, Buenos Aires, Argentina as an extension of NIH Grant R01DK46072 to Dr. Schwartz PUBLIC HEALTH RELEVANCE: Obesity is one of the most prevalent health problems in the world, particularly if it considered in relation to associated diseases such as diabetes. Improvement of our understanding of adipogenesis will ultimately contribute to the development of new therapeutic strategies for obesity and related disorders.